A study of regioselective and stereoselective functionalization reactions of azabicyclic molecules is proposed. Steric and lone pair coordination effects associated with the heteroatom and its attached substituents are to be exploited to control the stereochemistry of electrophilic and nucleophilic substitutions. As an example of the utility of the proposed stereochemical studies, stereoselective synthetic approaches to the antineoplastic and antibiotic agent 593A (NSC-135758), 2,5-piperazinedione, 3,6-bis-(5-chloro-2-piperidyl)-dihydrochloride are proposed starting from readily available isoquinuclidine or tropinone derivatives. 593A has been reported to have promising clinical activity against several types of advanced tumors in patients, most of whom had extensive prior chemotherapy. 593A is the first isolated prototype of the synthetic nitrogen mustards and may in its mechanism of action represent a new class of alkylating agents. The proposed synthetic approaches are applicable to structural, stereochemical, and functional group analogs of 593A.